The growth in electronic complexity and sophistication of consumer appliances has followed similar developments in office automation. Many appliances now contain microprocessors with memory and input/output to replace mechanical controls. These electronics initially were employed to lower manufacturing costs, but now are incorporated to enhance the appliance features. Examples include the operation of a washing machine for a variety of clothing materials with a single selection by the user, or a telephone set with memory and last-number redial.
The computer equipment in offices is now typically interconnected with a local area network so products manufactured by a variety of companies can communicate intelligently. This allows the equipment to be located where convenient for the user of the applications. Consumer appliance manufacturers are aware of the benefits that could accrue if different appliances could be interconnected in the house. An appliance would not need to be confined within one cabinet. Sensors, actuators, controls, and user interfaces could all be located throughout the house where appropriate for a task. Furthermore, the exchange of data among different appliances could enhance their capabilities.
The communication of data among the components of one appliance or among different appliances is technically possible, but not practically feasible. There are two key detriments to such a system, standards and appliance interface. Many manufacturers, trade associations, and government agencies recognize limitations imposed by a lack of standards. They also realize that solving these problems can open the development of a new industry termed "home automation" resulting in a variety of novel home automation products.
The Electronic Industries Association (EIA) is a United States trade association of manufacturers of consumer audio, video, computer, and telephone products. The EIA has organized a committee, called "Consumer Electronics Bus" (CEBus), to develop standards for interconnecting consumer appliances in a house. The CEBus committee is adopting the design principles of commercial local area networks to create communication protocols appropriate for the home environment.
The CEBus protocol description follows the established practice of the International Standards Organization (ISO). The ISO has defined a seven-layer model for a communication network, called the Open Systems Interconnect (OSI). This design abstraction allows heterogeneous products to exchange data over a network of arbitrary extent. The CEBus protocol is a published specification available to any manufacturer.
The CEBus protocol has been specialized to a typical residential environment. It accommodates six types of media, specifically infra-red, radio frequency, power line carrier, twisted-pair wires, coaxial cable, and fiber optic cable to provide a shared communication resource, termed a "bus," that may be used by many appliances.
The CEBus implements four of the "layers" of the OSI communications model:
layer 1: Methods of impressing digital data on each medium. PA1 layer 2: Methods of organizing binary data into meaningful messages (a sequence of bytes). PA1 layer 3: Methods of routing messages among appliances and among the six media. PA1 layer 7: A language for representing commands issued from one appliance to another to effect control.
The CEBus also provides a variety of media options so appliance manufacturers have a variety of migration paths for expanding appliance capabilities at the lowest cost and inconvenience. Nevertheless, manufacturers wishing to adopt CEBus face dilemmas regarding how an existing appliance can be made compatible and functional with CEBus, and how a manufacturer can adapt appliances to CEBus in "stages" without major redesign.
There are no known appliance apparatus that implement the CEBus protocol and can accommodate a variety of appliances without significantly disrupting the existing appliance functionality.